[133] I do not say that the assumption that these two groups of earwigs were of different ages is altogether an easy one; for of course, even in an insect whose metamorphosis is so simple as the earwig’s, consisting only in the acquisition of wings or wing-cases, we usually take it for granted that growth proceeds no more after the final stage, or “adult form” is attained, and further that this adult form is attained at an ap­prox­i­mate­ly constant age, and constant magnitude. But even if we are not permitted to think that the earwig may have grown, or moulted, after once the elytra were produced, it seems to me far from impossible, and far from unlikely, that prior to the appearance of the elytra one more stage of growth, or one more moult took place in some cases than in others: for the number of moults is known to be variable in many species of Orthoptera. Unfortunately Bateson tells us nothing about the sizes or total lengths of his earwigs; but his figures suggest that it was bigger earwigs that had the longer tails; and that the rate of growth of the tails had had a certain definite ratio to that of the bodies, but not necessarily a simple ratio of equality.

[134] Jackson, C. M., J. of Exp. Zool. XIX, 1915, p. 99; cf. also Hans Aron, Unters. über die Beeinflüssung der Wachstum durch die Ernährung, Berl. klin. Wochenbl. LI, pp. 972–977, 1913, etc.

[135] The temperature limitations of life, and to some extent of growth, are summarised for a large number of species by Davenport, Exper. Morphology, cc. viii, xviii, and by Hans Przibram, Exp. Zoologie, IV, c. v.

[136] Réaumur: L’art de faire éclore et élever en toute saison des oiseaux domestiques, foit par le moyen de la chaleur du fumier, Paris, 1749.

[137] Cf. (int. al.) de Vries, H., Matériaux pour la connaissance de l’influence de la température sur les plantes, Arch. Néerl. V, 385–401, 1870. Köppen, Wärme und Pflanzenwachstum, Bull. Soc. Imp. Nat. Moscou. XLIII, pp. 41–110, 1870.

[138] Blackman, F. F., Ann. of Botany, XIX, p. 281, 1905.

[139] For various instances of a “temperature coefficient” in physiological processes, see Kanitz, Zeitschr. f. Elektrochemie, 1907, p. 707; Biol. Centralbl. XXVII, p. 11, 1907; Hertzog, R. O., Temperatureinfluss auf die Ent­wick­lungs­geschwind­ig­keit der Organismen, Zeitschr. f. Elektro­chemie, XI, p 820, 1905; Krogh, Quantitative Relation between Temperature and Standard Metabolism, Int. Zeitschr. f. physik.-chem. Biologie, I, p. 491, 1914; Pütter, A., Ueber Tem­per­atur­koef­ficienten, Zeitschr. f. allgem. Physiol. XVI, p. 574, 1914. Also Cohen, Physical Chemistry for Physicians and Biologists (English edition), 1903; Pike, F. H., and Scott. E. L., The Regulation of the Physico-chemical Condition of the Organism, American Naturalist, Jan. 1915, and various papers quoted therein.

[140] Cf. Errera, L., L’Optimum, 1896 (Rec. d’Oeuvres, Physiol. générale, pp. 338–368, 1910); Sachs, Physiologie d. Pflanzen, 1882, p. 233; Pfeffer, Pflanzenphysiologie, ii, p. 78, 1904; and cf. Jost, Ueber die Reactions­geschwin­dig­keit im Organismus, Biol. Centralbl. XXVI, pp. 225–244, 1906.

[141] After Köppen, Bull. Soc. Nat. Moscou, XLIII, pp. 41–110, 1871.

[142] Botany, p. 387.